In the cellular wireless communications system known as the TD-SCDMA system (Time Division Synchronous Code Division Multiple Access), there can be communication between a base station such as a NodeB and user terminals within a certain area which is controlled by the base station, said area usually being referred to as a cell.
In one embodiment of the TD SCDMA system, the amount of data which is sent from the NodeB to the user terminal, the UE, is related to the quality of the link between the NodeB and the UE, i.e. the “down link”.
The quality of the down link is obtained by means of letting the NodeB use a dedicated channel for certain transmissions, and the received signal strength at the UE of these transmissions is then reported back to the NodeB.
In the TD SCDMA system, the dedicated channel which is used for quality measurements is known as the HS PDSCH channel (High Speed Physical Downlink Shared Channel), which is a shared channel in the system on which traffic data is sent.
Based on the received signal strength of the HS PDSCH at a UE, the UE will report a CQI (Channel Quality Information) to the NodeB. The CQI will comprise the RTBS, Recommended Transport Block Size, and the RMF, Recommended Modulation Format.
A TDD system is by definition a system which utilizes a number of time frames, each time frame being divided into time slots, and in the TD SCDMA system, the HS PDSCH channel can be used in more than one time slot per frame.
The UE in the TD SCDMA system reports the CQI per HS PDSCH, although the HS PDSCH can be used in more than one time slot per frame. This means that the down link channel quality in a number of time slots may be “lumped together” in one report, although the downlink channel conditions can vary between time slots. This may result in less than optimal choices of, for example, the parameters Transport Block Size and Modulation Format in some down link time slots to an UE.